In a manufacturing process of a semiconductor device, for example, a liquid processing process is known for removing particles or contaminants attached to a semiconductor wafer (“wafer”) by supplying a processing liquid such as a chemical liquid or deionized water (DIW) onto the surface of an object to be processed such as a wafer. A liquid processing apparatus performs the liquid processing by supplying the processing liquid onto the surface of the wafer while rotating the wafer. This kind of liquid processing apparatus includes, for example, a plurality of liquid processing units (e.g., 4 to 5 liquid processing sections) that can perform the same kind of liquid processing, transports the wafer to each of the liquid processing units by using a common transportation mechanism, and allows the plurality of liquid processing units to simultaneously perform the liquid processing of the wafer, in order to increase the number of processed wafers (throughput) per unit hour.
The liquid processing unit as described above includes, for example, a spin chuck placing and rotating the wafer and a cup provided to surround the wafer held on the spin chuck and collecting the processing liquid supplied and scattered onto the surface of the wafer. As the processing liquid, an acid chemical liquid or an alkaline chemical liquid may be used and a chemical liquid is selectively supplied to wafer W depending on the processing to be performed.
Japanese Patent Laid-Open Publication No. 2008-34490 discloses a liquid processing apparatus including a plurality of liquid processing units that are placed horizontally, and an exhaust line for an acid chemical liquid and an exhaust line for an alkaline chemical liquid. For example, on the exhaust line for the acid chemical liquid, an acid exhaust duct discharging an atmosphere in the liquid processing unit in acid processing for each of the liquid processing units is connected to each of the liquid processing units, an acid exhaust pipe is connected to each acid exhaust duct, and the atmosphere in each of the liquid processing units is collectively discharged by the acid exhaust pipe through each acid exhaust duct. Further, a valve which is opened and closed depending on the kind of the liquid processing in the corresponding liquid processing unit is provided in each acid exhaust duct. In addition, clean air flows into each of the liquid processing units from an airflow injection portion at all times and the cleanliness is maintained in each of the liquid processing units.